If Margie Profet is right -- they probably ate less vegetable matter when pregnant. For the uninitiated, Profet posits that that pregnancy sickness is an adaptation that serves to deter expectant mothers from ingestion of teratogens, hence protecting the developing nervous system of the fetus.

I happen to think she is onto to something. More on her here: http://en.wikipedia.org/wiki/Margie_Profet

PS my pregnant wife eats largely Paleo-ish, and had hardly any morning sickness.

He gets quoted around here a lot, and rightfully. So, not to sound like a parrot, but Robb Wolf mentioned in his 3rd or 4th Podcast talking about the importance of monitoring EPA/DHA levels during pregnancy. The Podcast was awhile ago, so I forget exactly what the science he quoted recommended. There was a conflict between lots of EPA and its antagonistic properties towards arachidonic acid and its development in fetal central nervous tissue.

Paleolithic woman was pregnant a lot less often than the Neolithic woman. Her lack of body fat simply made her less fertile. What they ate during pregnancy may well be forever be in the realm of speculation, but since pregnancy was a rare event and the survival of the tribe depended upon it, it isn't impossible that women were deliberately fattened up with carbs to increase fertility. Again, this is all speculation ...